Angelman syndrome is a genetic disorder that causes developmental disabilities and neurological problems, such as difficulty speaking, balancing and walking, and, in some cases, seizures. Frequent smiles and outbursts of laughter are common for people with Angelman syndrome, and many have happy, excitable personalities.

Angelman syndrome usually isn't detected until parents begin to notice developmental delays when a baby is about 6 to 12 months old. Seizures often begin when a child is between 2 and 3 years old.

People with Angelman syndrome tend to live a normal life span. But they may become less excitable and develop sleep problems that may improve with age. Treatment focuses on managing medical and developmental issues.

Characteristic Angelman syndrome signs and symptoms include:

Developmental delays, such as lack of crawling or babbling at 6 to 12 months, and intellectual disability

Lack of or minimal speech

Inability to walk, move or balance well (ataxia)

Frequent smiling and laughter

Happy, excitable personality

People who have Angelman syndrome may also have other signs and symptoms, including:

Seizures, usually beginning between 2 and 3 years of age

Stiff or jerky movements

Small head size, with flatness in the back of the head (microbrachycephaly)

Tongue thrusting

Light pigmentation in hair, skin and eyes (hypopigmentation)

Unusual behaviors, such as hand flapping and arms uplifted while walking

When to see a doctor

Most babies with Angelman syndrome don't show signs or symptoms of the disorder when they're born. The first signs of Angelman syndrome are usually developmental delays, such as lack of crawling or babbling, between 6 and 12 months.

If your child seems to have developmental delays or if your child has other signs or symptoms of Angelman syndrome, make an appointment with your child's doctor.

Angelman syndrome is a genetic disorder, most often caused by problems with a gene located on chromosome 15 called the ubiquitin protein ligase E3A (UBE3A) gene.

A missing or defective gene

You receive your genes, which occur in pairs, from your parents — one copy from your mother (maternal copy) and the other from your father (paternal copy). Your cells typically use information from both copies, but in a small number of genes, only one copy is active.

Normally, only the maternal copy of the UBE3A gene is active in the brain. Most cases of Angelman syndrome occur when part of the maternal copy is missing or damaged. In a few cases, Angelman syndrome is caused when two paternal copies of the gene are inherited, instead of one from each parent.

Angelman syndrome is rare. In most cases, researchers don't know what causes the genetic changes that result in Angelman syndrome. Most people with Angelman syndrome don't have a family history of the disease.

In a small percentage of cases, however, Angelman syndrome may be inherited from a parent, so a family history of the disease may increase a baby's risk of developing Angelman syndrome.

Complications associated with Angelman syndrome include:

Feeding difficulties. An inability to coordinate sucking and swallowing may cause feeding problems during the infant's early months. Your pediatrician may recommend a high-calorie formula to help your baby gain weight.

Hyperactivity. Moving quickly from one activity to another, short attention span, and keeping hands or a toy in their mouths may characterize children with Angelman syndrome. Hyperactivity often decreases with age, and medication usually isn't necessary.

Sleep disorders. People with Angelman syndrome often have abnormal sleep-wake patterns and need less sleep than normal. In some cases, sleep difficulties may improve with age. Medication and behavior therapy may help control sleep disorders.

Curving of the spine (scoliosis). Some people with Angelman syndrome develop an abnormal side-to-side spinal curvature over time.

Obesity. Older children with Angelman syndrome tend to have large appetites, which may lead to obesity.

Call your doctor if your baby or child isn't reaching expected developmental milestones or has other signs or symptoms common to Angelman syndrome. Your doctor may then refer you to a doctor who specializes in conditions that affect the brain and nervous system (neurologist).

Here's some information to help you get ready for your appointment.

What you can do

Write down signs or symptoms you've noticed in your child, and for how long.

Bring baby books and other records of your child's development to the appointment. Photographs and video recordings can be helpful.

List your child's key medical information, including other conditions for which your child is being treated, and the names of medications, vitamins or supplements that he or she takes.

Ask a family member or friend to join you for your child's appointment. If your child's doctor mentions the possibility of a developmental disorder, you may have great difficulty focusing on anything the doctor says next. Take someone along who can offer emotional support and can help you remember the information.

Write down questions to ask your doctor.

Questions to ask your child's doctor include:

What is likely causing my child's signs and symptoms?

Are there other possible causes for these signs and symptoms?

What tests does my child need?

Should my child see a specialist?

Questions to ask a specialist include:

Does my child have Angelman syndrome?

What are the possible complications of this condition?

What therapies are available?

What treatment do you recommend?

What is the long-term outlook for my child?

Should my child or I be tested for the genetic mutations associated with this condition?

What other specialists should my child see?

How can I find other families who are coping with Angelman syndrome?

Don't hesitate to ask other questions, as well.

What to expect from your doctor

A doctor who sees your child for possible Angelman syndrome is likely to ask you a number of questions, such as:

What are your child's signs and symptoms and when did you notice them?

Does your child have feeding problems?

Is your child reaching the expected, age-related physical milestones?

Have you noticed problems with balance, coordination or movement?

Does your child laugh, smile or express excitement more often than his or her peers?

Does your child express excitement with unusual physical behaviors, such as hand flapping?

Does your child communicate verbally?

How well does your child sleep?

Has your child had seizures? If so, how often?

Have any of your child's first-degree relatives — such as a parent or sibling — been diagnosed with Angelman syndrome?

Your child's doctor may suspect Angelman syndrome if your child has developmental delays and other signs and symptoms of the disorder, such as problems with movement and balance, small head size, flatness in the back of the head, and frequent laughter.

Confirming a diagnosis of Angelman syndrome requires taking a blood sample from your child for genetic studies. A combination of genetic tests can reveal the chromosome defects related to Angelman syndrome. These tests may look at:

Parental DNA pattern. This test, known as a DNA methylation test, screens for three of the four known genetic mechanisms that cause Angelman syndrome.

Missing chromosomes. Either a fluorescence in situ hybridization (FISH) test or a comparative genomic hybridization test (CGH) can show if portions of chromosomes are missing.

Gene mutation. Rarely, Angelman syndrome may occur when a person's maternal copy of the UBE3A gene is active, but mutated. If results from a DNA methylation test are normal, your child's doctor may order a UBE3A gene sequencing test to look for a maternal mutation.

There's no cure for Angelman syndrome. Research is focusing on targeting specific genes for treatment. For now, treatment focuses on managing the medical and developmental issues.

A team of health care professionals will likely work with you to manage your child's condition. Depending on your child's signs and symptoms, treatment for Angelman syndrome may involve:

Anti-seizure medication to control seizures

Physical therapy to help with walking and movement problems

Communication therapy, which may include sign language and picture communication

Behavior therapy to help overcome hyperactivity and a short attention span and to aid in development

Finding out that your child has Angelman syndrome can be overwhelming. You may not know what to expect, and you may worry about your ability to care for a child with medical concerns and developmental disabilities. There are resources that can help.

Work with a team

Find a team of doctors and therapists you trust to help you with important decisions about your child's care and treatment. These professionals can also help identify and evaluate appropriate resources in your area.

Consider a support group

Connecting with other families facing similar challenges may help you feel less alone. Ask your child's doctor for information about support groups and other helpful organizations in your area.

In rare cases, Angelman syndrome may be passed from affected parent to child through defective genes. If you're concerned about a family history of Angelman syndrome, or if you already have a child with Angelman syndrome, consider talking to your doctor or a genetic counselor for help planning future pregnancies.

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